The present invention relates to multi-pen recorders, and, more particularly, to a new and improved inking system for multi-pen recorders of the gravity-fed capillary type.
While various types of pressurized inking systems have been heretofore proposed in which the ink to a number of recorder pens is continuously pressurized, these systems have suffered from the disadvantage that the ink pen nib or tip must be pressed against the chart paper with a substantial force to prevent leakage from the pen tip due to the pressure exerted on the ink supply. This increased pressure increases the friction between the pen tip and the chart paper which not only reduces the lifetime of the pen tip but also slows down the pen's response time and increases the overall hysteresis of the system. Higher driving power which is required to obtain acceptable response times also requires a more powerful pen servo motor with a suitable feedback system.
As a result of these disadvantages many multi-pen recorders of the present day are of the gravity-fed capillary tube type and employ separate ink bottles for each pen. However, in these gravity-fed multi-pen systems some form of priming means is required for each ink supply to establish the initial flow of ink to each pen tip or to force ink through the tube in the event it becomes clogged. Previously, a rubber bulb, piston and cylinder, or bellows type arrangement has been used on the ink bottle cap of each of the ink bottles in a multi-pen gravity-fed capillary type recording system. In these arrangements it was easy for the ink bottle to become jostled and ink would get into the bulb or pump and then onto the user's hands. Also, with the pump located on the ink bottle cap there was little room left for a large ink tube since these ink bottle caps are of relatively small dimensions. Accordingly a relatively small diameter flexible tube is usually employed to connect the ink bottle cap with the pen which is mounted on the servo motor, these tubes being customarily 15 or 20 cm in length. These flexible tubes are usually made of a plastic material, which is quite permeable to the solvents in the ink solution. With such a length of thin-walled, small diameter tubing, after a few weeks of non-use of the inking system the dye in the ink would precipitate out and clog the tube.
Examples of various types of prior art inking systems for recorders are shown in the following U.S. Pat. Nos.: Hand 1,849,084; Bowditch 2,727,802; Cannon 2,800,385; Holloway 2,820,689; Dressel 2,821,919; Summers, Jr., et al. 3,046,556; Winston 3,060,429; Gill, Jr., et al. 3,185,991; Sivonen 3,247,519; Behmoras et al. 3,299,436; Hartai 3,355,424; Schweitzer 3,341,860; Sanderson et al. 3,371,350; Abrams et al. 3,614,940; Skafvenstedt et al. 4,053,901; and Brown, Jr. Reissue 25,692. The following U.S. Pat. Nos. are also cited as having general relevance to the present invention: Carter 626,750; England 1,907,763; Miller 2,769,573; Marwell et al. 3,208,639; and Kirch 3,418,054.
It is an object, therefore, of the present invention to provide a new and improved ink priming system for a multi-pen recorder of the gravity-fed capillary tube type wherein one or more of the above discussed disadvantages of prior art arrangement is eliminated.
It is another object of the present invention to provide a new and improved ink priming system for a multi-pen recorder wherein means are provided for selectively supplying gas under pressure to any one of the ink reservoirs associated with each recording pen of the recorder.
It is a further object of the present invention to provide a new and improved ink priming system for a multi-pen recorder wherein a manifold common to the recording pens is provided to which gas under pressure is supplied and individual control valves are provided for selectively supplying gas from the manifold to the ink bottle associated with a particular recording pen so as to prime this pen.
It is another object of the present invention to provide a new and improved non-clogging inking system for use in a recorder wherein the ink, which comprises dye in a suitable solvent, is connected to the movable recorder pen element through a flexible tubular member which is permeable to the ink and has a length such that the concentration of the dye in the ink at the end of the tubular member which is connected to the recorder pen does not exceed its saturation value.
It is a further object of the present invention to provide a new and improved non-clogging inking system for use in a recorder or the like, wherein a flexible tube is employed to connect the ink supply with the recorder pen, said tube being sufficiently short that evaporation of the ink solvent through the walls of the tube is accompanied by diffusion of dye back to the ink supply so the concentration of dye in the ink at the end of the tubular member near the recorder pen does not exceed saturation.
Briefly considered, the present invention relates to an ink priming system for a multi-pen recorder of the gravity-fed capillary tube type in which individual ink bottles are provided for each recorder pen. A gas manifold, common to all of the ink bottles, is connected to each of the ink bottles through a suitable control valve so that gas which is supplied to the manifold under pressure may be selectively applied to any ink bottle to force ink from that bottle out of the corresponding pen to prime it. As soon as the recording pen is primed and the control valve is released, the gas pressure is bled off so that the system thereafter acts as a normal gravity-fed capillary tube recording system. Therefore, during normal usage of the recording pen the ink is not pressurized and hence the pen nib may press relatively lightly on the chart paper and may be driven by a relatively low powered pen motor as compared to conventional pressurized inking systems.
In accordance with the further aspect of the invention, a non-clogging inking system is provided for each recorder pen by utilizing a short length of flexible thin walled tubing to supply ink to the movable recording pen element. The length of this permeable, thin walled tube is sufficiently short that evaporation of the ink solution through the walls of the tube is accompanied by diffusion of the dye back to the ink bottle so that the concentration of dye in the ink at the end of the tubular member which is connected to the recorder pen does not exceed saturation value. As a result, the recorder pen may remain motionless for long periods of time without causing precipitation of the dye and clogging of either the tubular member or the recorder pen.